Development of a Standardized Method for Measuring Bioadhesion and Mucoadhesion That Is Applicable to Various Pharmaceutical Dosage Forms.

Although some methods for measuring bioadhesion/mucoadhesion have been proposed, a standardized method is not yet available. This is expected to hinder systematic comparisons of results across studies. This study aimed to design a single/systematic in vitro method for measuring bioadhesion/mucoadhesion that is applicable to various pharmaceutical dosage forms. To this end, we measured the peak force and work of adhesion of minitablets, pellets, and a bioadhesive emulsion using a texture analyzer. Porcine tissue was used to simulate human stomach/skin conditions. The results of these formulations were then compared to those for formulations without the bioadhesive product. We conducted a case study to assess the stability of a bioadhesive emulsion. The results for the two parameters assessed were contact time = 60 s and contact force = 0.5 N at a detachment speed of 0.1 mm/s. Significant differences were observed between the bioadhesive and control formulations, thus demonstrating the adhesive capacity of the bioadhesive formulations. In this way, a systematic method for assessing the bioadhesive capacity of pharmaceutical dosage forms was developed. The method proposed here may enable comparisons of results across studies, i.e., results obtained using the same and different pharmaceutical formulations (in terms of their bioadhesion/mucoadhesion capacity). This method may also facilitate the selection of potentially suitable formulations and adhesive products (in terms of bioadhesive properties).

Effect of emollients on UV filter absorbance and sunscreen efficiency.

The idea of increasing the performance of sunscreens without adding more UV-filters is very attractive. Early studies reported an influence of solvents on the absorbing properties of UV-absorbers which was shown to be connected to the solvent polarity. However, the polarity differed a lot between tested solvents and most were unsuitable UV-filter solubilizers. The aim of the present study was to focus exclusively on emollients pertinent for sunscreens and investigate their impact on the performance of UV-filter combinations. The UV absorbance of Bis-ethylhexyloxyphenol Methoxyphenyl Triazine, Ethylhexyl Triazone, Diethylamino Hydroxybenzoyl Hexyl Benzoate, and Ethylhexyl Methoxycinnamate was measured in suncare relevant emollients comprising C12-15 Alkyl Benzoate, Dibutyl Adipate, Caprylic/Capric Triglyceride, Coco-caprylate, Isopropyl Myristate, Dicaprylyl Carbonate. The wavelength of maximum absorbance (λmax) and specific extinction at λmax (E1,1 (λmax)) were assessed for each UV-filter - emollient system. The performance of market relevant UV-filter combinations based on the studied UV-filters was simulated for each emollient with a computational method using the absorbance values measured for each UV-filter - emollient system. The difference in polarity of emollients led to a 2-3 nm bathochromic shift and a variation of the E1,1 (λmax) ranging from 4 to 20% for tested UV-filters. The emollient type showed nearly no influence on the sun protection factor (SPF) of market relevant UV-filter combinations probably due to a different influence an emollient shows on the UVB filters resulting in cancelling of the corresponding effect. Conversely, for all UV-filter combinations the UVA protection decreased with a decrease in the emollient polarity. Whilst the SPF was not impacted by standardly used cosmetic oils, the results advocate to use polar emollients to optimize the UVA protection. This is of advantage since polar emollients better dissolve crystalline UV-filters. From tested emollients, Dibutyl Adipate performed the best for both SPF and PPD factors.

Implementation of a functional endpoint to the zebrafish embryotoxicity test to evaluate craniofacial abnormalities.

The inclusion of a read-out to detect functional consequences of craniofacial alterations in the zebrafish embryotoxicity test will allow to evaluate these alterations which are difficult to assess morphologically, and to detect alterations in cranial nerves functions leading to impairment of jaw movements. In this study we have established an ingestion test in zebrafish larvae younger than 120 hpf. To overcome the challenge of evaluating larvae which still do not present independent feeding behaviour, we have tested the ability of 72, 96 or 102 hpf larvae to ingest food mixed with fluorescent microspheres under several conditions (dark/light, with/without shaking) to find the best experimental set-up for the test. We have included the investigation of two substances as potential positive controls: ketoconazole and tricaine. Ketoconazole 10 µM exposure during development produced significant embryotoxic effects including a characteristic craniofacial alteration pattern consisting in impaired development of brain, nasal cavity, mouth opening and jaw, as well as a significant decrease in food intake. Tricaine exposure at 380 µM during the food availability period significantly decreased the food intake. The method proposed will be a useful alternative tool to animal testing to detect compounds inducing adverse effects on craniofacial development.

Analysis of photokinetics of 2'-ethylhexyl-4-methoxycinnamate in sunscreens.

2'-Ethylhexyl-4-Methoxycinnamate (EHMC), also designated as octinoxate, is an oily UV-absorber used in sunscreens for the protection of human skin against solar UV-radiation and represents one of the most employed UVB absorbers for that application. In water-in-oil emulsions EHMC was adjusted at a constant overall concentration, while changing the EHMC concentration in the oil droplets by adding a non-absorbing oil. In that way the EHMC concentration could be varied at constant optical thickness. Here we show that the kinetics of the photoreaction follows a second-order rate law, in line with the UV-induced [2 + 2]-cycloaddition reaction mechanism known for this UV absorber. The second-order rate constant decreased with higher overall EHMC concentration. This can be explained by the fact, that at higher overall concentration of the UV absorber not every EHMC molecule will absorb a photon due to the increased optical density, so that on average less photons are absorbed per molecule. On the other hand, the rate constant increases with decreasing polarity of the surrounding oil. Since the molar fraction of the trans-isomer of EHMC is augmented at lower polarity, more photons are absorbed in this case, as the strength of the absorption band of the trans-isomer is significantly higher than that of the cis-isomer. In conclusion, our experiments show that a high polarity of the oil phase and a high concentration of EHMC are advantageous for the photostability of this compound.